1. Field of the Invention
This invention relates to epoxide ring opening products having a defined residual epoxide oxygen content and to a process for their production by reaction of epoxides with nucleophiles in the presence of medium-strength acids.
2. Discussion of Related Art
Long-chain polyol compounds containing two or more free hydroxyl groups and a percentage of epoxide groups are valuable raw materials for the production of polymers, for example polyesters, alkyd resins or polyurethane foams.
They are preferably produced from olefins or unsaturated fatty compounds which are epoxidized in a first step. In a second step, the epoxides formed are subjected to ring opening with nucleophiles, for example water or alcohols, resulting in the formation of substances bearing vicinally arranged substituents of which one is a hydroxyl group. This opening of the oxirane ring is the subject of a number of publications.
For example, U.S. Pat. No. 4,057,589 describes a process for the production of tetrols by reaction of unsaturated diols with peracetic acid and subsequent hydrolysis of the epoxides formed at temperatures of at least 120.degree. C.
EP 0 127 810 A1 describes the sulfuric-acid-catalyzed ring opening of epoxides of unsaturated fatty acid esters with alcohols and their subsequent saponification.
DE 3 246 612 A1 describes a process for the production of modified triglycerides in which epoxidized fats or oils are reacted with monohydric or polyhydric alcohols in the presence of sulfuric acid, phosphoric acid or sulfonic acids. The reaction is terminated after a conversion of 20 to 80 mol-%, based on the epoxide groups, by destruction and/or removal of the catalyst and/or the alcohol component.
The catalyst-free pressure hydrolysis of short-chain epoxides containing 3 to 8 carbon atoms and fatty epoxides containing 16 to 22 carbon atoms with water is the subject of EP 0 257 243 A2, EP 0 340 587 A2 and EP 0 361 080 A1.
Finally, EP 0 257 332 B1 describes a process for the continuous production of 1,2-diols in which epoxides are subjected to pressure hydrolysis with water in the presence of acidic catalysts.
However, the production of polyol compounds having a residual epoxide oxygen content by known processes is attended by a number of disadvantages:
Thus, where pressure hydrolysis technology is applied, unwanted secondary products are likely to be formed, for example by transesterification reactions. In addition, the ring opening of the epoxides by this process can only be carried out with water if the necessary outlay on equipment is not to exceed the profitability of the process. Accordingly, only a limited number of products can be obtained by pressure hydrolysis.
If, by contrast, the ring opening of the epoxide compounds is carried out in the presence of acidic catalysts, the residual epoxide oxygen content has to be adjusted by removal or neutralization of the catalyst at a certain epoxide value or by removal of one of the reaction components, for example the nucleophile. This involves increased outlay on equipment.
Accordingly, the problem addressed by the present invention was to provide an improved process for the production of epoxide ring opening products having a defined residual epoxide oxygen content which would be free from the disadvantages mentioned above.